Method of making inner tubes



Patented July 24, 1 928.

UNITED STATES PATENT OFFICE.

nfmns'r w. MELVIN, 0F MILWAUKEE, WISCONSIN, VASSIGNIOR T0 THE-FISK RUBBER COMPANY, OF GHIGOPEE FALLS, MASSACHUSETTS, A coRPonAmoN 0F MASSA- CHUSETTS.

No Drawing canization.

According to One conventional method the raw tube is formed by forcing warm, plastic rubber through a circular die of a tubing machine. A suitable length of so formed tube is then drawn onto a cylindrical mandrel and wrapped with strips of fabric. The mandrel with the wrapped tube is then vulcanizedin .a suitable heater. The purpose of the wrapping is to hold the raw stock firmly against the mandrel and prevent the entrance of steam between the tube and mandrel during vulcanization.

It is among the objects of my invention to provide a method which does away-with the necessity of wrapping the tubes which is a costly .and time consuming operation andin which the stock is held on the mandrel with a uniform tension. 7

Other and further objects will be apparent from the following specification and claim.

In carrying out my improved method I tube the stock in a conventional tubing machine but to a diameter substantially less METHOD OF MAIHNG INNER TUBES.

Application filed December 17, 1924. Serial No. 756,622.

than the diameter of the-mandrel upon' which the tube is to be cured. I thenstretch the raw tube. onto the mandrel preferably by the application of compressed air between the tube and the mandrel. The tube when released onto the mandrel hugs the clatter uniformly throughout its length and effectually prevents the entrance of steam between the tube and mandrel during vul canization without the necessity of any The vulcanization may be car- 40 wrapping. ried out in any conventional manner.

I claim:

The method of making inner tubes for pneumatic tires which comprises, tubing the stock to desired shape but. of a cross sec- 'tional diameter less than the cross sectional diameter of the mandrel upon which it is to .be cured by an amount such that when the tube is stretched upon-the mandrel the'tendency of the tube to hug the mandrel is 60' sufficient by and of itself to prevent the penetration of the vulcanizing fluid between the tube and the mandrel, stretching the so formed tube onto the mandrel and subjecting the tube to vulcanization.

v In testimonywhereof I have signed my I name to the above specification.

ERNEST MELVIN. 

